The opinion extols the virtues of longstanding limits that Congress has placed on corporations and unions. It gives a completely unnecessary "historical prologue" (slip. op. at 8) explaining the unique purposes that corporate/labor union separate funds requirement serves. This discussion supports Congress's need to regulate the rise in "issue ads."

But it's hardly unusual for Souter to include a "completely unnecessary 'historical prologue'" in his opinions. It seems to be rather common.

Who could forget the opening paragraph of Souter's majority opinion in the 1995 case of Hurley v. Irish-American Gay Group of Boston. The question was whether the organizers of the St. Patrick's Day parade in Boston had a First Amendment right to exclude a pro-gay group from marching. Souter began the opinion by recounting 250 years of the history of holiday celebrations in Boston, including a citation to a book published in 1902 detailing the history of St. Patrick's Day celebrations between the years 1737 and 1845:

March 17 is set aside for two celebrations in South Boston. As early as 1737, some people in Boston observed the feast of the apostle to Ireland, and since 1776 the day has marked the evacuation of royal troops and Loyalists from the city, prompted by the guns captured at Ticonderoga and set up on Dorchester Heights under General Washington's command. Washington himself reportedly drew on the earlier tradition in choosing "St. Patrick" as the response to "Boston," the password used in the colonial lines on evacuation day. See J. Crimmins, St. Patrick's Day: Its Celebration in New York and other American Places, 1737-1845, pp. 15, 19 (1902); see generally 1 H.S. Commager & R. Morris, The Spirit of 'Seventy Six 138-183 (1958); The American Book of Days 262-265 (J. Hatch ed., 3d ed. 1978). Although the General Court of Massachusetts did not officially designate March 17 as Evacuation Day until 1938, see Mass. Gen. Laws 6:12K (1992), the City Council of Boston had previously sponsored public celebrations of Evacuation Day, including notable commemorations on the centennial in 1876, and on the 125th anniversary in 1901, with its parade, salute, concert, and fireworks display.

An even more outstanding example is the opening section of Souter's majority opinion last year in Verizon Communications, Inc. v. FCC, where the question was whether the FCC had come up with an appropriate economic methodology for calculating the lease rates that local phone companies have to use when renting their equipment and lines to their competitors.

Most Justices would have begun by looking at the governing statute, the 1996 Telecommunications Act. But not Justice Souter. Instead, pages 4 to 17 of the slip opinion were devoted to an exhaustive and excruciatingly detailed history of rate regulation in the United States. All of this historical background, though, was irrelevant to the actual case at hand. As Souter himself said in the conclusion of that section, "Congress called for ratemaking different from any historical practice" when it passed the 1996 Act.

If you read the tea leaves carefully in that opinion, it appears that a couple of other Justices were not too happy with Souter's historical excursion. Thomas, for example, joined in Sections III and IV of Souter's opinion -- which happened to be the entirety of Souter's legal analysis and holdings. In other words, the sections that Thomas refused to join were Section I (procedural history of the case) and Section II (historical background). I've never before seen a Supreme Court opinion where a Justice joined in the legal analysis and the holding, but refused to join the facts section. (Justice Scalia similarly refused to join Sections I and II, although he didn't entirely agree with Souter's reasoning in a later section of the opinion.)